Vancouver came in dead last when it came to the amount of cannabis use per capita, which may come as a shock to some. Perhaps even more surprisingly, however, is that Halifax was the leader in the amount of cannabis use per capita.

With this in mind, a number of factors weigh on the overall results. For example, the report notes that, “the wastewater treatment plant in Halifax was situated in the core area of the city and as a result, the consumption of cannabis measured there may not represent the city’s entire metropolitan population.”

Further, temperature, acidity and the presence of industrial chemicals or bacteria in the sewer system of each city could also alter the results.

Canadian Cannabis Sewage

So, how exactly are cannabis levels measured in wastewater?

Researchers utilized a new form of research called “wastewater-based epidemiology” in order to measure the metabolites that people eliminate from their bodies.

“When people consume cannabis or tetrahydrocannabinol (THC), the main psycho-active constituent of cannabis, their bodies process the cannabis into metabolites (THC-COOH, in the case of THC) that are later eliminated from the body and typically flushed into the municipal wastewater system,” reads the report.

“Through direct analysis of the concentrations of THC-COOH in wastewater, Statistics Canada can estimate the total mass of cannabis consumed.”

The pilot project covered areas that covered 15 wastewater treatment plants in five large urban centres across Canada, which represent nearly 8.4 million people. As such, it made the project one of, if not the, continuous WBE pilot tests to date.